scholarly journals High Quality Echelle Observations of T Tauri Stars

1988 ◽  
Vol 132 ◽  
pp. 99-104
Author(s):  
G. Basri
Keyword(s):  
High Resolution ◽  
Line Profile ◽  
T Tauri Stars ◽  
Young Stars ◽  
Emission Lines ◽  
Current Understanding ◽  
General Nature ◽  
High Quality ◽  
T Tauri ◽  
Made In

This is a very brief review of the high resolution line profile work that has been done on very young stars. The spectral anamolies peculiar to these stars are mentioned, with some discussion of what may give rise to them. The Hα line is discussed most extensively, as the most work has been done with it. While progress has been made in understanding the general nature of T Tauri spectra, there are very large gaps in our current understanding of the emission lines from these stars.

scholarly journals A Comparative Study of Lithium Abundances, Radial Velocities, and Emission Lines in Pre-Main Sequence Visual Binaries

1992 ◽  
Vol 135 ◽  
pp. 63-65
Author(s):  
Eduardo L. Martín ◽  
Rafael Rebolo ◽  
Antonio Magazzù
Keyword(s):  
High Resolution ◽  
Comparative Study ◽  
Spectral Properties ◽  
Main Sequence ◽  
Angular Separation ◽  
T Tauri Stars ◽  
Radial Velocities ◽  
Emission Lines ◽  
T Tauri ◽  
First Results

AbstractHigh resolution (R ~ 20000) spectroscopic observations of visual pairs of T Tauri stars (TTS) in the spectral range 655-675 nm, and 385-405 nm for some systems, are reported. Good seeing allows us to resolve pairs with minimum angular separation of ~ 2″. The radial velocities, overall spectral properties and detection of the Li I line are used to decide whether the components of the binaries are likely to be gravitationally bounded. In this paper we present first results on a subset of our sample: 3 visual companions are not TTS, namely DL Tau/c, GG Tau/c(SW) and NTTS 45251+3016/c. The star GG Tau/c(S) is confirmed as a T Tauri star. The system UZ Tau is probably composed of at least 4 components. The star 1E0255.3+2018 (Fleming et al. 1989), previously thought to be single, is found to be a close visual binary. Finally, lithium abundances for the PMS components of 6 binaries are presented and their consistency with theoretical expectations is briefly discussed.

Spectroscopic Signatures of Microjets

1997 ◽  
Vol 182 ◽  
pp. 63-72 ◽  
Author(s):  
J. Solf
Keyword(s):  
High Resolution ◽  
Velocity Component ◽  
T Tauri Stars ◽  
Emission Lines ◽  
Low Velocity ◽  
Disk Wind ◽  
Physical Conditions ◽  
T Tauri ◽  
Spectroscopic Signatures ◽  
Kinematic Properties

High-resolution long-slit spectroscopy of forbidden emission lines is used to investigate on a sub-arcsecond scale the spatial and kinematic properties and the physical conditions of the mass outflows from T Tauri stars in the immediate vicinity of the outflow source (microjets). Special attention is given to the case of DG Tau. The data permit us to distinguish physically different outflow components: (1) a high-velocity component (HVC) attributed to a fast jet, (2) a low-velocity component (LVC) attributed to gas entrained by the jet, and (3) a near-rest-velocity component (NRVC) attributed to a slow disk wind and/or disk corona.

scholarly journals Actvity on T Tauri Stars

1995 ◽  
Vol 151 ◽  
pp. 221-222
Author(s):  
Erik Gullbring ◽  
Gösia F. Gahm ◽  
Heinz Barwig ◽  
Peicheng Chen
Keyword(s):  
Time Scales ◽  
High Speed ◽  
T Tauri Stars ◽  
Young Stars ◽  
Tauri Star ◽  
Emission Lines ◽  
Base Line ◽  
Short Term ◽  
T Tauri ◽  
Short Term Variability

We have made a detailed investigation of the short-term variability of the classical T Tauri star BP Tauri in UBVRI. Data were collected from the Wendelstein Observatory in 1991, 1992 and 1993 with time resolutions down to 1 sec. The 0.8m telescope was equipped with a fiber-fed fifteen channel high-speed photometer (Barwig et al. 1987). Observations (in UBV) were also collected in China at the Yunnan and Shanghai Observatories to get a long base line in time. To search for differences in the properties between the brightness variations of classical T Tauri stars (CTTS) and T Tauri stars with weak emission lines (WTTS) we performed simultaneous photometry (in the UBV and Strömgren systems) and spectroscopy of 6 young stars during two observing periods at ESO La Silla. The study concerned mainly short-term variability on time-scales of minutes to a few hours. The sample contained two CTTS, SY Ori and VW Cha; three WTTS, San 1, SZ Cha and ADA 481 and one post-T Tauri candidate, HD 70309B.

scholarly journals Variability of young stars: Determination of rotational periods of weak-line T Tauri stars in the Cepheus-Cassiopeia star-forming region

2009 ◽  
Vol 330 (5) ◽  
pp. 482-492
Author(s):  
A. Koeltzsch ◽  
M. Mugrauer ◽  
St. Raetz ◽  
T.O.B. Schmidt ◽  
T. Roell ◽  
...  
Keyword(s):  
T Tauri Stars ◽  
Young Stars ◽  
Weak Line ◽  
Star Forming ◽  
T Tauri

scholarly journals Oh Observations Near the Reflection Nebulae Ngc 2068 and Ngc 2071

1974 ◽  
Vol 60 ◽  
pp. 301-302
Author(s):  
L. E. B. Johansson ◽  
B. Höglund ◽  
A. Winnberg ◽  
Nguyen-Q-Rieu ◽  
W. M. Goss
Keyword(s):  
Dust Cloud ◽  
T Tauri Stars ◽  
Emission Lines ◽  
Class I ◽  
Reflection Nebula ◽  
Cosmic Background ◽  
T Tauri ◽  
Reflection Nebulae

Narrow OH emission lines at 1667 MHz, apparently from a Class I source, have been observed near the reflection nebula NGC 2071. The region contains many T Tauri stars. OH emission corresponding to the dust cloud north and east of NGC 2024 is also seen. At 1720 MHz the dust cloud component appears in absorption; presumably the isotropic 2.7 K cosmic background is being absorbed.

scholarly journals Characterising the surface magnetic fields of T Tauri stars with high-resolution near-infrared spectroscopy

2019 ◽  
Vol 630 ◽  
pp. A99 ◽  
Author(s):  
A. Lavail ◽  
O. Kochukhov ◽  
G. A. J. Hussain
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Magnetic Fields ◽  
Large Scale ◽  
Near Infrared ◽  
Field Measurements ◽  
T Tauri Stars ◽  
Small Scale ◽  
Surface Magnetic Field ◽  
T Tauri

Aims. In this paper, we aim to characterise the surface magnetic fields of a sample of eight T Tauri stars from high-resolution near-infrared spectroscopy. Some stars in our sample are known to be magnetic from previous spectroscopic or spectropolarimetric studies. Our goals are firstly to apply Zeeman broadening modelling to T Tauri stars with high-resolution data, secondly to expand the sample of stars with measured surface magnetic field strengths, thirdly to investigate possible rotational or long-term magnetic variability by comparing spectral time series of given targets, and fourthly to compare the magnetic field modulus ⟨B⟩ tracing small-scale magnetic fields to those of large-scale magnetic fields derived by Stokes V Zeeman Doppler Imaging (ZDI) studies. Methods. We modelled the Zeeman broadening of magnetically sensitive spectral lines in the near-infrared K-band from high-resolution spectra by using magnetic spectrum synthesis based on realistic model atmospheres and by using different descriptions of the surface magnetic field. We developped a Bayesian framework that selects the complexity of the magnetic field prescription based on the information contained in the data. Results. We obtain individual magnetic field measurements for each star in our sample using four different models. We find that the Bayesian Model 4 performs best in the range of magnetic fields measured on the sample (from 1.5 kG to 4.4 kG). We do not detect a strong rotational variation of ⟨B⟩ with a mean peak-to-peak variation of 0.3 kG. Our confidence intervals are of the same order of magnitude, which suggests that the Zeeman broadening is produced by a small-scale magnetic field homogeneously distributed over stellar surfaces. A comparison of our results with mean large-scale magnetic field measurements from Stokes V ZDI show different fractions of mean field strength being recovered, from 25–42% for relatively simple poloidal axisymmetric field topologies to 2–11% for more complex fields.

scholarly journals Quasicyclic Light Changes in Three Low Mass T Tauri Stars

1977 ◽  
Vol 42 ◽  
pp. 66-71
Author(s):  
H. Mauder
Keyword(s):  
Variable Stars ◽  
T Tauri Stars ◽  
Emission Lines ◽  
T Tauri ◽  
Cyclic Variations ◽  
Low Mass ◽  
Photographic Survey ◽  
Objective Prism

During a photographic survey of the Chamaeleon T association in 1971/1972, evidence was found for quasiperiodic light changes of three variable stars, see Mauder and Sosna (1975). The period of 6.2 days for SY Cha is well seen, the periods of 7 days for VZ Cha and of 8 days for TW Cha are less pronounced. Intrinsic variations are present in addition to the cyclic variations. The three stars were classified by Hoffmeister (1963) as T Tauri type stars from their light variations. Objective prism spectra obtained by Henize and Mendoza (1973) confirm this classification, they found conspicuous emission lines. For SY Cha and TW Cha they got slit spectra, too, which show the typical veiling. The stars SY Cha, TW Cha and VZ Cha have been observed in the UBV system from 1974 March 12 until 1974 March 22, using the ESO standard photometer. In Figures 1 - 3 the light and colour curves are given for SY Cha, TH Cha and VZ Cha. Each point is a mean of generally 8 to 12 integrations, each integration lasting 5 seconds.

scholarly journals The Infrared Companions of T Tauri Stars: Clues to the Formation and Early Evolution of Binaries

2001 ◽  
Vol 200 ◽  
pp. 265-274 ◽  
Author(s):  
Chris D. Koresko ◽  
Christoph Leinert
Keyword(s):  
T Tauri Stars ◽  
Young Stars ◽  
Early Evolution ◽  
Young Stellar Objects ◽  
Physical Status ◽  
Stellar Objects ◽  
T Tauri ◽  
Mode Of Development ◽  
Source Of Information

Infrared companions are young stellar objects with unusual properties gravitationally bound to more or less typical T Tauri stars. As such they promise to be the source of information on either a particular phase in the development of young stars or on a particular mode of development. We discuss the observed properties of infrared companions as well as attempts to explain their physical status with the aim to see how much of solid conclusion has been obtained so far.

scholarly journals High-resolution X-ray spectroscopy of T Tauri stars in the Taurus-Auriga complex

2007 ◽  
Vol 468 (2) ◽  
pp. 443-462 ◽  
Author(s):  
A. Telleschi ◽  
M. Güdel ◽  
K. R. Briggs ◽  
M. Audard ◽  
L. Scelsi
Keyword(s):  
High Resolution ◽  
T Tauri Stars ◽  
X Ray ◽  
T Tauri

scholarly journals The accretion disk paradigm for young stars

2007 ◽  
Vol 3 (S243) ◽  
pp. 1-12 ◽  
Author(s):  
Claude Bertout
Keyword(s):  
Accretion Disk ◽  
Indirect Evidence ◽  
Circumstellar Disks ◽  
T Tauri Stars ◽  
Young Stars ◽  
Young Stellar Objects ◽  
Recent Attempt ◽  
Disk Model ◽  
Stellar Objects ◽  
T Tauri

AbstractAccretion and magnetic fields play major roles in several of the many models put forward to explain the properties of T Tauri stars since their discovery by Alfred Joy in the 1940s. Early investigators already recognized in the 1950s that a source of energy external to the star was needed to account for the emission properties of these stars in the optical range.The opening of new spectral windows from the infrared to the ultraviolet in the 1970s and 1980s showed that the excess emission of T Tauri stars and related objects extends into all wavelength domains, while evidence of outflow and/or infall in their circumstellar medium was accumulating.Although the disk hypothesis had been put forward by Merle Walker as early as 1972 to explain properties of YY Orionis stars and although Lynden-Bell and Pringle worked out the accretion disk model and applied it specifically to T Tauri stars in 1974, the prevailing model for young stellar objects until the mid-1980s assumed that they experienced extreme solar-type activity. It then took until the late 1980s before the indirect evidence of disks presented by several teams of researchers became so compelling that a paradigm shift occurred, leading to the current consensual picture.I briefly review the various models proposed for explaining the properties of young stellar objects, from their discovery to the direct observations of circumstellar disks that have so elegantly confirmed the nature of young stars. I will go on to discuss more modern issues concerning their accretion disk properties and conclude with some results obtained in a recent attempt to better understand the evolution of Taurus-Auriga young stellar objects.

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